North Korean leader Kim Jong Un was not happy with President Donald Trump's remark at the NATO meeting in London that the U.S. would use force against his regime if necessary. 

In a statement published by the state-run North Korean Central News Agency, army chief of staff Pak Jong Chon said Kim was "displeased" with the "undesirable remarks" and warned that North Korea and the U.S. "are still technically at war and the state of truce can turn into an all-out armed conflict any moment." 

"One thing I would like to make clear is that the use of armed forces is not the privilege of the U.S. only," Pak said. 

When asked by reporters about North Korea's continued missile tests on Tuesday, Trump said the U.S. has the most powerful military in the world and that he would use it against Kim's regime "if we have to." 

He added that Kim "likes sending rockets up, doesn't he?" 

"That's why I call him Rocket Man," Trump said, referring to a nickname he had given Kim amid their belligerent exchanges in 2017. 

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One North Korean official threatened to bring back Kim's own past insult for Trump. 

North Korean 1st Vice Foreign Minister Choe Son Hu said Thursday that her ministry "cannot contain its displeasure" at Trump's remarks and warned that if Trump keeps it up, he "will again show the senility of a dotard." In September 2017, Kim vowed to "tame the mentally deranged U.S. dotard," referring to Trump. 

But on Tuesday, Trump stressed that he and Kim have a "good relationship." 

"I like him, he likes me," Trump said. "We'll see what happens. It may work out, it may not." 

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Pak agreed on the importance of the relationship between Trump and Kim, saying "the only guarantee that deters physical conflict from flaring up" is "the close relations between the top leaders" of the two countries. 

"But recently, the U.S. president said that he may use armed forces in clear reference to the DPRK, even though he attached preconditions," Pak said, referring to North Korea by its formal name, the Democratic People’s Republic of Korea. "This greatly disappointed me." 

He warned that "such elated spirit and bluffing" could agitate North Korea and threaten the fragile peace and that an attack on the regime would be "a horrible thing for the U.S." 

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North Korea has issued several belligerent statements toward the U.S. in recent weeks while also conducting short-range missile tests. 

In April, Kim declared an end-of-the-year deadline for progress to resume in the negotiations between the two countries. But little progress has been made in the denuclearization talks since a summit in Vietnam between Trump and Kim broke down in February. 

Kim said that if the deadline was not met, he would seek a "new path." Last month, the regime threatened to resume testing of ballistic missiles. 

Prior to Trump's comments on Tuesday, a North Korean official reiterated Kim's deadline and said, "it is entirely up to the U.S. what Christmas gift it will select to get."

Contributing: The Associated Press 

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